Every package that is developed should provide tests to guarantee it gives the expected behavior.

Our tool of choice for tests is Jest by Facebook which provides us with the ability to add custom matchers, snapshot testing and parallelizes our test runs.

All packages have a yarn test command which you should run before sending a PR or pushing to GitHub to make sure all tests are passing.
You could use yarn test:watch to listen to changes on the files and run the tests automatically.

Additionally, we provide a variant (yarn test:debug) that enables the Node debugger.